Lead refining



March 1936. J. o. BETTERTON ET AL 2,032,788

LEAD REFINING Fi led Oct.

10, 1932 5 Sheets-Sheet 1 INVENTORS N Jase a Baler/an j/ara' 7 Zrfiedgj' ATTORNE March 1936. J. o. BETTERTON ET AL 2,032,788

LE IIIIIIII NG Filed Oct. 10, 1932 3 Sheets-Sheet 2 I N g NNNNNN 0R5 Jase a fiellerlon- 91 551: E leedayf a t- M ATTORNEYS March 1936. J, o. BETTERTON ET AL 2,032,788

LEAD REFINING Filed Oct. 10, 1932 3 Sheets-Sheet 3 I ATTORN EY$ above the surface of the bath and the pump and Patented Mar. 3, 1936 PATENT OFFICE LEAD REFINING Jesse o. Betterton and Yurii E. Lebedefl, Me-

tuchen, N. J., assignors to American smelting and Refining Company, New York, N. Y., a corporation of New Jersey Application October 10, 1932, Serial No. 637,052

8 Claims.

The invention relates to purifying metals, such as lead.

The invention may be employed for removing various impurities in the refining of lead or other metals, and in the case of lead, for example, it may be used for removing silver, copper, bismuth, etc.

According to one manner of practicing the invention, solid reagent is placed in a basket or container and immersed in the molten lead bath. A pump may be provided to circulate small portions of the lead bath at a time through the reagent, causing a dross .to be formed, which floats to the surface of the bath. In the case of debismuthizing the lead, the reagent may be calcium or magnesium, or the alloys of these metals with lead.

The apparatus for performing the drossing operation may comprise a suitable framework adapted to rest on the kettle holding the lead bath. This framework may support a pump and a motor for driving-it, and the container or basket for holding the reagent. The motor is located reagent container is immersed in the bath.

After sufiicient bismuth has been removed, the pump may be used to discharge the purified lead into'another kettle, leaving the dross in the first kettle.

An additional batch of impure lead may then be introduced into the first kettle, into which the remaining dross may be stirred by an ordinary stirring machine, as the primary reagent for forming the primary dross on the new batch of lead. This primary dross may be skimmed from the bath in the usual manner, after which the above described method and apparatus may be used to form the secondary dross.

If desired, the new batch of lead may be treated directly by the method and apparatus above described to form additional dross, the dross being allowed to accumulate until such time that it must be removed.

Various other features and advantages of the invention will be apparent from the following particular description and-from an inspection of the accompanying drawings.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, and the manner in which it may be carried out, may be better understood? by referring to the following description taken in connection with the accompanying drawings forming a. part thereof, in which Fig. 1 is a side elevation of the apparatus for carrying out the method of the invention;

Fig. 2 is an elevation taken at right angles to the elevation of Fig. 1;

Fig. 3 is a section on the line 3-3 of Fig. 2;

Fig. 4 is an end view of the reagent container; and

Fig. 5 is a side view thereof.

In the following description and in the claims, various details will be identified by specific names for convenience, but they are intended to be as generic in their application as the art will permit.

Like reference characters denote like parts in the several figures of the drawings.

In the drawings accompanying and forming part of this specification, certain specific disclosure of the invention is made for purposes of explanation, but it will be understood that the details may be modified in various respects with out departure from the broad aspect of the invention.

Refering now to the drawings, the refining apparatus comprises a kettle l8 containing the molten lead or other metal to be purified whose level is indicated by i I. This kettle is constructed and supported in a manner well known in the art of purifying lead.

Resting on the kettle ll! is a framework, indicated-by l2, and adapted to be lifted by a crane (not shown) from the kettle It] to another kettle, if desired. The framework l2 comprises a horizontal platform portion l3 and a depending portion it. This framework is made of structural steel and is properly braced and reinforced for strength.

. The horizontal portion l3 supports a drive mo- I tor l5 which is preferably electric. The. electric motor It drives gearing in gear box It through coupling H. The gearing in gear box l6 drives pump shaft l8, which in turn drives the lead cirby U-members 25 under the surface of the bath.

The container (Figs. 4 and 5) is made up of a cylindrical wall 26 having a back wall 21 adjacent the discharge pipe 23 and a front cover 28 connected to the body of the container by hinge 29. The cover or door 28 is made up of suitable vertical and-horizontal rods suitably welded or otherwise secured together, forming a foraminous or perforate wall. For holding the door closed, apertured ears 30 are provided through which are driven wedges 3|. The container 24 is filled with reagent, indicated' by bars 32, which in the case of debismuthizing lead may be of alkaline earth metal, such as metallic calcium or magnesium.

For transferring purified lead from the kettle I, an additional pipe 33 may be provided. The coupling 22 is then used to disconnect the discharge pipe 23 from discharge pipe 2| and the transfer pipe 33 is substituted for the former. This permits the same pump IE! to transfer the purified lead into another receptacle which may be another kettle, indicated by 34, leaving the dross in the kettle It to be used with a new batch of lead to be purified.

To carry out the process 'according to one form of the invention, the lead to be purified is introduced into the kettle H1 at the usual temperature used for removing the particular impurities.

In the case of debismuthizing, the alkaline earth metals, such as metallic magnesium or calcium. or both, or their alloys with lead, are stirred into the lead bath in the usual way to form the primary dross which floats on the top of the bath. This dross is skimmed off the bath in the usual manner.

For removing the remaining bismuth, the framework I2 is placed in position after the reagent container 24 has been filled with the same reagents used to form the primary dross. The submerging of the reagent, which may be in bar form, below the surface of the bath prevents oxidation of the reagent. The pump I9 is then started and moderate circulation is caused by pumping the molten lead from the kettle into the reagent container, resulting in a thorough mixing of the bath. This mixing does not have to be vigorous and therefore does not require excessive power.

While the circulation of the bath is moderate, the weight of the lead is sufficient to produce enough momentum to wash the reagent clean of accumulating insoluble reaction products. A certain amount of these reaction products which comprise principally magnesium bismuthide and which would tend to adhere to the refining re agent, thereby impeding contact between the reagent and the lead in the bath, would collect on the body of the magnesiumand in the basket, were it not for the'circulation of the bath. This circulation, however, produces a uniform concentration of the reagent in the bath and by washing the surface thereof free from reaction products maintains continuously fresh the surfaces of contact between the reagent and the bath, while forcing the reaction products to the surface of the bath. The pumping is continued as the bath cools,

causing the secondary dross to form until practically the freezing temperature of the bath is reached. The pipe 33 is then substituted for the pipe 23 and the pump is used to transfer the purified lead into the other kettle or container 34.

.. The secondary drosses or crusts floating on the surface of the purified lead being frozen remain in the kettle l0.

A new batch of lead to be purified is then introduqed into the kettle III, the remaining dross acting as the primary reagent to form a new primary dross. This dross or reagent is stirred into the bath by a stirring machine (not shown) in the usual manner.

The primary dross thus formed is skimmed from the surface of the bath in the usual manner, after which the framework I2 is replaced and the secondary drossing operation carried out, as above described.

The above cycle is then repeated, the purified lead always being transferred out of the kettle l0, and the secondary dross, formed by the secondary drossing operation, acting as the primary reagent to form tthe primary dross of the new batch of lead to be purified.

The present invention overcomes many disadvantages ofprior processes where the reagent for the secondary drossing operation was stirred in by a stirring machine, and the secondary dross had to be removed by hand. These secondary drosses were sometimes quite heavy and required skilled labor to remove them.

Another advantage of the invention is the decrease of oxidation of the secondary drosses since these drosses are not removed in small portions, with resulting exposure of each portion to the air. Another advantage of the present invention is that less reagent is required since less is lost through oxidation.

Another advantage of the present invention is the more thorough removal of the impurity from the lead. This follows because the temperature of the bath is maintained more uniform throughout its mass as the temperature is decreased practically to the freezing temperature of the bath.

It will be understood that the process and apparatus, above described, may be applied to the refining of metals other than lead and for removing from lead other impurities than bismuth.

If desired, the reagent placed in the basket or container 24 may be magnesium, or magnesiumlead alloy alone. The pump l9 may be used to circulate the lead to dissolve the magnesium. After the magnesium is dissolved, the calcium. or calcium-lead alloy may be added either by placing the same in the container 24 or directly into the kettle. In either case the pump will be again started slowly to dissolve the calcium.

\ If desired, the stirring machine for obtaining the primary dross may be omitted and all of the dross may be obtained by direct use of the above described apparatus. In this case, after sufiicient impurities have been separated from the lead bath in the form of a dross, the purified lead 'may be pumped into another container, as de-' scribed above, and a new batch of impure lead placed in the kettle. This lead may be purified by additional reagent using the above apparatus without removing the, dross already accumulated. After the second batch of lead is purified, it may be removed and a third batch admitted. This process may be carried on for several cycles until so much dross has accumulated that it must be removed.

While certain novel features of the invention have been disclosed and are pointed out in the annexed claims, it'will be understood that various into a second kettle, leaving the secondary dross in the first kettle, adding a new batch of impure lead to the first kettle and stirring into the new batch the dross remaining in the first kettle to form the primary dross, skimming off the primary dross thus formed, placing additional reagent under the surface of the bath, circulating small portions of the bath at a time through the submerged reagent as above, and repeating the above cycle.

2. The process of refining lead which comprises adding a reagent, such as calcium or calcium and magnesium to a kettle of impure lead, stirring in the reagent to obtain a primary dross, skimming off said primary dross, placing further reagent under the surface of the bath, circulating small portions of the bath at a time through the submerged reagent while cooling the bath to obtain a secondary dross, pumping out the purified lead from beneath the surface into a second kettie, leaving the secondary dross in the first kettle, adding a new batch of impure lead at a higher temperature to the first kettle and stirring into the new batch the dross remaining in the first kettle to form the new primary dross, skimming off the primary dross thus formed as before, placing additional reagent under the surface of the bath, circulating small portions of the bath at a time through the submerged reagent as above and repeating the above cycle.

3. The process of refining lead which comprises adding a reagent, to a kettle of impure lead, stirring in the reagent to obtain a primary dross, skimming off said primary dross, placing further reagent under the surface of the bath, circulating small portions of the bath at a time through the submerged reagent while cooling the bath to obtain a secondary dross, removing the purified lead from beneath the surface into a second kettle, leaving the secondary dross in the first kettle, adding a new batch of impure lead at a higher temperature to the first kettle and stirring into the new batch the dross remaining in the first kettle to form the new primary dross, skimming off the primary dross thus formed as before, placing additional reagent under the surface of the bath, circulating small portions of the bath at a time through the submerged reagent as above and repeating the above cycle.

4. The process of refining lead which comprises placing below the surface thereof a reagent, circulating small portions of the lead bath at a time through the submerged reagent to form a secondary dross, removing purified lead from beneath the surface, leaving the secondary dross to act as primary reagent for a new batch of impure lead to form primary dross thereon.

5. 'In apparatus for the refining of metals, a kettle adapted to contain molten metal to be purified, a removable framework comprising a transverse part resting on the top of the kettle and a depending part extending toward the bottom of the kettle, a drive motorand a gear box on said transverse part, a circulatory pump on said depending part, a drive shaft extending from said gear box to said pump, a foraminous container suspended from said transverse portion and immersed in the molten metal, and a discharge pipe extending from said pump to said container.

- 6. In apparatus for the refining of metals, a kettle adapted to contain molten metal to be purified, a removable frame comprising a trans-. verse part resting on the top of the kettle and a depending part extending toward the bottom of the kettle, a drive motor and a gear box on said transverse part, a circulatory pump at the bottom of said depending part, a drive shaft extending from said gear box to said pump, a connector at said transverse portion, said pump. having an inlet at the bottom of the kettle and a discharge pipe extending up to said connector, a foraminous container suspended from said transverse portion and immersed in the molten metal, a supply pipe extending from said connector to said container, and a transfer pipe extending from said connector to another kettle.

7. In refining metal by reacting same with a reagent capable of combining with the impurities to form a dross of lower specific gravity than the metal, the improvement which comprises confining the reagent beneath the surface of 2. molten bath of the metal, circulating portions of the metal through the reagent at a time thereby yielding a dross containing the impurities, withdrawing the refined metal from below the surface of the bath thereby leaving the dross, reacting additional impure metal with said dross in situ, skimming the resulting dross and further refining said additional metal according to the above cycle.

8. The improved process for refining lead which comprises confining the refining agent in a stationary, foraminous container beneath the surface of a molten bath of the lead to be refined and circulating the lead through the stationary container in contact with the reagent thereby effecting reaction between the reagent and im-- purities in the lead, the circulation being conducted at such velocities as are suflicient to continuously wash the reagent free from reaction products.

JESSE O. BET'IERTON. YURI]; E. LEBEDEFF. 

